The present invention relates to a sliding member comprising an overlay layer made of a Bi based alloy.
A plain bearing, in which a bearing alloy layer made of a Cu alloy or an Al alloy is lined on a steel backing layer, has been often used in internal combustion engines of automobiles or the like. In order to improve conformability of such a bearing with a mating shaft, an overlay layer is formed on the surface of the bearing alloy layer with or without an intermediate layer.
Conventionally, the overlay layer has been made of a soft Pb alloy, occasionally a Sn alloy. The intermediate layer has been often made of a Ni alloy, a Ag alloy and so on.
However, it is undesirable to use Pb if possible, because it is a pollutant to the environment. In order to solve the Pb problem, various researches have been conducted, wherein one example has been proposed to use Bi as an alternative to Pb. However, Bi is hard and inferior in conformability. In order to solve this problem, there has been proposed one idea to make the overlay layer with a Bi alloy which contains one or more additive elements selected from the group of Sn, In and Ag (see, for example, JP-A-11-50296).